Ca^2+ is implicated as a second messenger in coupling various stimuli such as hormone, gravity and light. To determine whether or not plant hormones mobilize calcium with different action, we investigated the cytosolic Ca^2+ changes by IAA and zeatin in the protoplasts isolated from elongating mesocotyl of maize. IAA increased the influx of Ca^2+ due to the calcium channel opening, which was confirmed by using verapamil, calcium channel blocker. On the other hand, zeatin increased the cytosolic Ca^2+ by promoting the efflux of Ca^2+ derived from cellular organelles. These results suggest that different calcium flux induced by IAA and zeatin plays a role in appropriate response resulting in increase of cell elongation or repression of cell elongation.